Merge pull request #2434 from Shopify/fix-return-type

Fix render extension return type

Author: vividviolet

.changeset/unlucky-cycles-invite.md

@@ -0,0 +1,6 @@
+---
+'@shopify/ui-extensions': patch
+---
+
+Fix return type for RenderExtension to optionally return a clean up function
+Remove unused RunnableExtension interface for Admin

packages/ui-extensions/src/surfaces/admin/registration.ts

@@ -1,9 +1,5 @@
 export interface RenderExtension<Api> {
-  (root: HTMLElement, api: Api): Promise<() => void>;
-}
-
-export interface RunnableExtension<Api, Output> {
-  (api: Api): Output | Promise<Output>;
+  (root: HTMLElement, api: Api): Promise<void | (() => void)>;
 }
 
 export interface ExtensionRegistrationFunction<ExtensionTargets> {